Efficacy of cobalt 60 radiotherapy in dogs with pituitary-dependent hyperadrenocorticism.
OBJECTIVE
To determine efficacy of cobalt 60 radiotherapy in dogs with pituitary-dependent hyperadrenocorticism (PDH) that have detectable tumors but no neurologic abnormalities.


METHODS
Case series.


METHODS
6 dogs with PDH that had a detectable pituitary mass on magnetic resonance images.


METHODS
Radiation was delivered in 11 fractions during a 3.5-week period for a total dose of 44 Gy. Clinical signs were evaluated, a urinalysis and ACTH stimulation test were performed, and urine cortisol-to-creatinine ratio and plasma endogenous ACTH concentration were measured before, immediately after, and 1, 3, 6, 9, and 12 months after radiotherapy. Magnetic resonance imaging was repeated 1 year after radiotherapy.


RESULTS
Clinical signs of hyperadrenocorticism resolved in 3 dogs but recurred in 2 of the 3. Clinical condition of 2 dogs improved but did not return to normal. One dog did not improve. Results of ACTH stimulation tests and urine cortisol-to-creatinine ratios correlated with clinical signs. Plasma endogenous ACTH concentration transiently decreased in all 6 dogs. One year after radiotherapy, size of tumors was decreased by 25% in 2 dogs; in the other 4 dogs, tumors could no longer be detected. None of the dogs developed neurologic abnormalities. Adverse effects of radiotherapy were mild.


CONCLUSIONS
Radiotherapy did not result in adequate control of clinical signs of hyperadrenocorticism in 5 of 6 dogs, but size of pituitary tumors was dramatically reduced. Thus, it may be reasonable to recommend radiotherapy in dogs with PDH that have pituitary tumors for which greatest vertical height is 8 mm or more.
Goossens
M M
MM
Veterinary Medical Teaching Hospital, Davis, CA, USA.
Feldman
E C
EC
Theon
A P
AP
Koblik
P D
PD
D000308:Adrenocortical Hyperfunction / Q000209:etiology / Q000532:radiotherapy / Q000662:veterinary*; D000818:Animals; D003037:Cobalt Radioisotopes / Q000627:therapeutic use; D004283:Dog Diseases / Q000209:etiology / Q000532:radiotherapy*; D004285:Dogs; D005260:Female; D008279:Magnetic Resonance Imaging / Q000662:veterinary; D008297:Male; D010910:Pituitary Irradiation / Q000662:veterinary*; D010911:Pituitary Neoplasms / Q000150:complications* / Q000175:diagnosis
D003037:Cobalt Radioisotopes